Electric switch and closing and opening means therefor



July 18, 1933- G. A. BURNHAM 1,918,378

ELECTRIC SWITCH AND CLOSING AND OPENING MEANS THEREFOR11111/111111zllflrlllzllll/zlllll.

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Filed May 5l, 1929 Patented July is, 1933 UNITED STATES PATENT OFFICEGEORGE A. BURNHAM, OF SAUGUS, MASSACHUSETTS, ASSIGNOR TO CONDITELECTRICAL MANUFACTURING CORPORATION, A CORPORATION OF MASSACHUSETTSELECTRIC SWITCH AND CLOSING AND OPENING MEANS THEREFOR Application ledMay 31,

This invention relates to electric switches and to controlling apparatusand systems therefor.

A switch is designed to carry its rated load and to open and close theloaded circuit successfully if the time intervals between successiveopening operations is not too short. If the switch is opened repeatedlyunder a heavy load, with but a small interval between successiveopenings, the contacts become hot an-d burn, and destructive arcing cantake place. For many purposes, and especially for the control of motors,it is not essential that the switch be opened repeatedly at a rapidrate, and such operation can in fact be harmful to the switch, the motorand to the circuit. Consequently, an object of this invention is toprovide a switch and operating devices therefor so arranged that asuitably long period of time must intervene between successive openingsof the switch upon heavy load.

A further object of the invention is the provision of a switch andcontrol devices therefor so arranged that after the switch has opened,it cannot be reclosed before the expiration of a predetermined timeinterval.

The usual type of motor starting switches with which this invention ismore particularly concerned are closed electrically and are held closedby an electro-magnet, the circuit of which is controlled -by push buttoncircuit controllers.

A further object of the present invention is the provision of anlelectrically-closed motor starting switch and controlling switches orcircuit controllers therefor and means so arranged that the circuitcontrollers are ineffective to effect successive openings of the motorstarting switch within a predetermined time interval.

A further object of the invention is the provision of anelectrically-operated motor starting switch and circuit controllerstherefor with means so arranged that the circuit controllers areineffective to effect the reclosing of the switch except after apredetermined time interval after it is opened under load.

A further object of the invention is gen- 1929. Serial No. 367,340.

erally to improve the construction and operation of electric switchesand control systems and apparatus therefor.

Fig. 1 is a more or less diagrammatic representation of anelectrically-operated motor starting switch and its connections with thepush button circuit controllers therefor, the construction of the pushbutton controllers being shown in section and arranged in accordancewith the present invention.

Fig. 2 is a section along line 2-2 of Fig. l.

Fig. 3 is a view similar to Fig. l, but i1- lnstrating a modifiedmechanism for obtaining `delayed reclosing of the switch.

Fig. 4 is a more or less diagrammatic representation of a switch whereinthe means to delay the reclosing of the switch for a predetermined timeinterval after the reclosing ofttihe switch is incorporated directlytherewi The switch with which the present invention is associated ismore or less diagrammatically shown and includes a movable bridgingmember 10 which is adapted to move upwardly and engage and bridge thestationary contact members 12 of one of the circuit conductors 14 of theherein shown single phase circuit that includes the other conductor 16.The switch may control the supply of power to any power consuming deviceas the motor 18.

While the switch here shown is illustrated as being in but one conductorof the circuit,

it is to be understood that the switch can be in all conductors of thecircuit, as is common practice.

The bridging member 10 is here shown as mounted on an insulating bar 20carried by the switch arm 22 which latter is pivoted loosely at its freeend to one leg of an electromagnet 24 which has an actuating winding 26.The arrangement is such that when said winding is energized theelectro-magnet attracts the lever 22' and moves the bridging member intoengagement with the fixed contact members 12. thereby closing theswitch. The switch is held closed by maintaining the electro-magnetenergized. The circuit of the electro-magnet is controlled by a pair ofpush button controlled circuit controllers,

there being a push button 28 which is arranged to insure the initialenergization of the magnet and thereby the closing of the switch and asecond push button 30 which serves to effect the de-energization of themagnet and the opening of the switch. The switch closing push button 28controls .a normally-open circuit controller and to th1s end, has aspring 32 that supports the movable contact member 34 of the controllernormally above and out of contact with the fixed contact members 36 and38 of the controller., The push button 28 can be depressed manually tobridge said fixed contact members but when the pressure is removed, thespring 32 carries the push button upwardly and interrupts the circuit.The switch o ening push button 30 controls a normally-c osed circuitcontroller and has a spring 40 which maintains the movable contactmember 42 of the controller normally in bridging contact with the fixedcontact member 38 and a second fixed contact member 44 of thecontroller. When the push button 30 is depressed the bridging member 42is moved away from said contact members 38 and 44, thereby interruptingthe closing circuit of the switch. When the pressure on the push buttonis removed, the spring 40 returns the push button to its aforesaidcircuit closing position.

One terminal of the winding 26 of the electro-magnet is connected by aconductor 46 to the conductor 16 of the power circuit. The otherterminal of the winding 26 is connected by a conductor 48 with the fixedcontact member 44 and thus through the normally closed openingcontroller with the fixed contact member 38 of the closing controller.The other fixed contact member 36 of the closing controller is connectedby the conductor 50 with the other conductor 14 of the power circuit.Thus, when the closing controller is depressed, the electro-magnetwinding is placed across the power circuit and is thus energized and theswitch is closed. The closing of the switch serves to establish a shuntcircuit for the electro-magnet around the closing circuit controller sothat the push button can be released and its circuit broken withoutcausing the switch to open. This shunt circuit includes a conductor 52which is connected with the fixed contact member 38 of the closingcontroller and with the bridging member 10 of the switch. Thus, when theswitch is closed, and the circuit through the closing controller isinterrupted, the circuit through the electro-magnet winding ismaintained complete through the conductor 52. The closing circuitcontroller and the shunt circuit 52 are in seriesvwith the openingcontroller so that when the push button thereof is depressed, theelectro-magnet circuit is opened and the switch thus falls open. Whenthe switch is opened, the shunt circuit is opened, so that the switchstays open .until rccloscd by the second depression of the closing pushbutton.

The two circuit controllers are usually contained in a suitable casing54 which may be disposed in any suitable position regardless ly underload either to satisfy his curiosity as to the operative condition ofthe switch or in an attempt to keep the switch closed on such heavyoverload or other abnormal conditions that the protective devicesinstantly open the switch after its reclosure. Such rapidly repeatedopenings of the switch on heavy load are detrimental to the switch sinceinsuflicient time is thus given to permit the contact members of theswitch to cool 0H and the arc gases to be dissipated. Consequently, withrapidly repeated openings under load, the contact members become hot anddestructive' arcing can take place. Moreover, the rapidly repeatedclosings and openings of the switch under heavy load or short circuitobviously can be detrimental to the power circuit and to the apparatusassociated therewith. Consequently, means are herein provided to preventthe rapidly repeated opening of the switch under heavy overload exce tafter the expiration of predetermined time intervals following eachopening operation, and specifically to prevent the reclosing of theswitch after it is opened until the expiration of such time interval.

Figs. 1 and 2 illustrate an arrangementv 58 operab e therein andmaintained normally in elevated position by suitable means as the spring60. The cylinder is fixedly supported beneath the push button 28 and thepiston 58 has a piston rod or stem 62 which extends upwardly between thecontact members 36 and 38 and is terminated immediately under but freefrom fixed engagement with said push button. The arrangement is suchthat as said push button and its bridging member` is depressed, it willalso depress said stem and the piston 58 and thereby compress the spring60. The dashpot is so arranged, as by having a check valve 64 whichcontrols the flow of Huid between opposite sides of the piston throughthel passage 66, that the piston can descend freely in the cylinder buthas its upward movements under the action of the spring 60 retarded. Thetime that it takes the piston to move upwardly into its normal elevatedposition is the period that the push button 28 and its circuitcontroller is locked in elevated and unoperative position; and this timecan be varied in any suitable manner not necessary to illustrate herein,since it is generally known in the art.

The dashpot controls a latch 68, see especially Fig. 2, which isvertically extended upwardly beside the movable contact member 34 of thecontroller button and is adapted, immediately after the push button hasbeen restored to its elevated position to move under said contact memberand to be held in such position until the dashpot operates to move itaway from such position. To this end, the latch, which can be made ofinsulating material, or otherwise suitably insulated from the controlcircuits, is pivoted at its lower end on a support and has a spring 72or other biasing means which normally tends to hold it yieldingly underand in the path of downward movement of the push button. The latch has aforwardly extended arm 74 that overlies the stem 62 of the dashpot and ashoulder or abutment 76 of said stem. The arrangement is such that whenthe stem 62 is in its normal elevated position, the shoulder 76 thereofengages the arm 74 and thus holds the latch 68 in an unoperatedposition, the spring 60 of the dashpot being stronger than the spring 72of the latch.

When, however, the push button is depressed to close the switch, thestem 62 is also depressed, thereby freeing the latch. While the pushbutton instantly returns to its elevated position, the piston of thedashpot is delayed in its upward movement. Thus, the latch 68 can snapinto position under the push button and hold it in elevated positionagainst a second downward movement until the piston is moved upwardlysufiiciently for the abutment 76 to move the latch out of lockingrelation with the push button. The time period during which the pushbutton is locked out of operation can be anything desired by a suitabledesign or adjustment of the dashpot. The time may be five seconds, orten seconds, or more or less, but is adapted to be such at least as togive the switch contacts time enough' to cool oil prior to successiveopenings under load so that the rated load of the switch can beinterrupted successively an indefinite number of times without damage tothe switch, and also without damage to the apparatus controlled by theswitch.

Fig. 3 illustrates essentially the same arrangement of switch and pushbutton circuit controllers as shown in Fig. 1 except that the pushbuttons and especially the closing push button 28 is located in a well78 of the casing 54 so that it is in best position to be depressed onlywhen it is at the top of the well. Instead of positively locking thestarting push button in an elevated and inoperative position for apredetermined period of time as in Fig. 1, means are illustrated in Fig3 to delay the return of the push button into position for a secondoperation.

Said delaying means includes a ratchet wheel 80 which is connectedthrough a oneway clutch 82 with a spur gear 84 that is driven by a rack86 of said push button. The ratchet wheel is engaged by a pivoted pawl88 having the timing weights 90 the position of which from the pivotalcenter of the pawl determines the rate of vibration of the pawl. The oneway clutch 82 is so arranged that the push button 28 can be depressedfreely to effect the closing of the switchl without operating theratchet wheel and pawl. l

The upward movement of the push button under action of its spring 32,however, causes the engagement of the clutch and thus the driving of theratchet wheel and pawl. The rate of upward movement of the push buttonis thus governed by the rate of vibration of the pawl so that the pushbutton is returned to its elevated position only after a predeterminedperiod of time.

In Fig. 4 means are associated directly with the switch to prevent theclosing thereof until after the expiration of a suitable time after ithas opened. To this end. the arm or lever 22 of the switch is adapted tobe locked in switch open position by a latch 108 for a suitable periodof time so that the switch can not be reclosed during such time. Thelatch is held normally in lockingr relation with the switch arm by aspring 110 but is held normally out of locking position by being engagedby the stem 112 of a piston 114 working within a dashpot cylinder 116and being urged for upward movement by a spring 118, the latter springoverpowering the spring 110. The switch arm 22 has a horizontallyslidable latch finger 120 that engages a projection 124 which removesthe latch from engagement with the dashpot stem thus permitting it tomove slowly upwardly under the urge of the spring 118. iVhen the stem112 is moving downwardly, the latch 108 is free to move into a positionabove the switch arm 22 so as to hold it in switch open position untilthe stem 112 moves upwardly to move the latch out of holding positionwhereupon the switch is then free to be reclosed. The time that it takesthe piston of the dashpot to move the latch 108 away from holdingposition is thus the time that the switch is prevented from reclosing.This time can be varied by suitable design or adjustments to the dashpotin the usual manner.

I claim:

1. 'lhe combination of an electric switch having electromagnetic closingmeans for it including a winding that is adapted to be maintainedenergized to hold the switch closed, a manually-operated circuitcontroller to open the circuit of said winding and thereby to open theswitch, a second manually-operated circuit controller to close thecircuit of said winding and thereby to close the switch immediately, andtime-governed locking mechanism operated by one operation of said secondcontroller having means to prevent a second operation thereof untilafter the expiration ot' a. predetermined time period.

2. An electro-magnetically operated electric switch having closing meansfor it including a winding that is adapted to be maintained energized tohold the switch closed, a circuit controller arranged to close thecircuit of said winding to close the switch, and time-governed meansoperated by one operation of said controller to delay the completion ofa second ope-ration thereof including a latch arranged to hold thecontroller in an inoperative osition, and means operated by said controler arranged to move said latch away from holding position after apredetermined time period.

3. An electro-magnetically-operated electric switch including a Windingthat is adapted to be maintained energized to hold the switch closed, acircuit controller arranged to close the circuit of said winding toclose the switch, and time-governed means operated by one operation ofsaid controller to delay the completion of a second operation thereofincluding a latch arranged to hold the controller in an inoperativeposition, a dashpot having a plunger which is depressed by theswitch-closing movement of said controller, and means to move saidpiston slowly in the opposite direction and into engagement with saidlatch, whereby to remove said latch from controller-holding position.

4. An electro-.magnetically-operated electric switch including a windingthat is adapted to be maintained energized to hold the switch closed, acircuit controller adapted to close the circuit of said winding to closethe switch, means normally biased into a position to lock the controllerin an unoperated position thereof, and timc-governed means etectiveafter an interval following an operation of said controller to removesaid locking means from locking position.

5. An electro-magnetically-operated electric switch including a windingthat is adapt-ed to be maintained energized to hold the switch closed, acircuit controller adapted to close the circuit of said winding to closethe switch, means normally biased into a position to lock the controllerin an unoperatxal position thereof, and time-governed means actuated bya switch-closing operation of said controller and eli'ective after apredetermined time following such operation1 thereof to remove saidlocking means from locking position.

G. A circuit controller having electro-inagnetic closing means for itincluding a winding adapted to be maintained energized to hold theswitch closed, a manually-operative circuit controller to close thecircuit of said winding and close the switch, said controller includinga member movable between circuit-open and circuit-closed positions, alatch biased for movement into position to hold said member frommovement in one direction, a timing member normally holding said latchaway from holding position disposed in position to be engaged and movedaway from said latch by a movement ot said member, whereby to permitsaid latch to move into a position to hold said member from movement,and means to return said timing member slowly to its original positionfree from said member to reengage said latch and remove it from holdingposition.

GEORGE A. BURNHAM.

